FBI hunts for 3 siblings sought in bank robbery, cop shoot-out

The brother, sister and half-brother are being called "the Dougherty family"

A federal arrest warrant ties them to an armed bank robbery in Georgia

They are suspects in the attempted murder of a Florida police officer during a shoot-out

The three siblings, all in their 20s, haven't been seen publicly since Tuesday

(CNN) -- Authorities are using digital billboards across the Southeast in their manhunt for three siblings, all in their 20s, who are wanted for an alleged armed bank robbery in Georgia and are suspects in the attempted murder of a Florida police officer, the FBI said Saturday. The crimes occurred Tuesday.

"I'm not going to compare them to Bonnie and Clyde -- I'll let you do that if you like -- but they are certainly very clear in demonstrating their threat to both law enforcement and the public," FBI special agent Stephen Emmett told CNN Saturday.

"It's not very often that we have advance warning like this of potential problems with law enforcement encountering individuals. They made it very clear that they are going to be a problem," added Emmett, a spokesman for the FBI's Atlanta office.

Hundreds of digital billboards from Florida to Kentucky to Texas are posting the photographs of the three siblings and their white, four-door, 2006 Subaru Impreza with the New York license tag "FBE 5900," Emmett said.

The siblings are considered armed and dangerous because an AK-47 type assault rifle and an apparent machine pistol were used in a Valdosta, Georgia, bank robbery Tuesday, the FBI said. A U.S. magistrate issued warrants for the arrest of the three siblings in connection to the robbery, the FBI said.

Also, the three siblings are suspects in the attempted murder Tuesday of a Zephyrhills, Florida, police officer that allegedly occurred 200 miles from and five hours before the Georgia bank robbery, the FBI said.

The officer wasn't injured, though occupants in a vehicle fired numerous rounds during a chase reaching up to 100 miles per hour, according to the Pasco County, Florida, Sheriff's office. One round went into the police vehicle's tire, disabling the automobile, the sheriff's office said.

The last public sighting of the three siblings was Tuesday, the day of the crimes, said Doug Tobin, spokesman for the Pasco County Sheriff's office.

"We're concentrating on the Southeast and East corridor because that's where they have family right now, but they could be anywhere," Tobin said Saturday.

Pasco County Sheriff Chris Nocco has urged the siblings to turn themselves in. Among the states that will carry the police messages on digital billboards are Florida, Texas, Louisiana, Mississippi, Alabama, Georgia, Arkansas, South Carolina, Kentucky, Tennessee and New York, the sheriff's office said.

"Although we continue to seek a peaceful resolution, the actions of the Dougherty family prove this will end otherwise," Nocco said in a statement. "I ask that everyone pray for the law enforcement officers who will eventually engage these suspects, for they will have to do everything possible to ensure that the Doughertys' violent rampage comes to an end."

The two brothers have been living in the same rented residence the past three years in Lacoochee, Florida, which is located in Pasco County, the sheriff's office said. Their sister, who had been living with her boyfriend in Orlando, just began staying with her brothers, the sheriff's office said.

The three siblings have criminal records, the sheriff's office said.

With the most extensive record of the three, Ryan Edward Dougherty has had 14 felony arrests since 2007, including for alleged burglary, destroying evidence and probation violation, according to the sheriff's office.

His live-in girlfriend owned the vehicle that he and his two siblings are believed to be driving, the sheriff's office said. After the girlfriend filed a complaint about her missing car, an arrest warrant for grand theft auto was issued Friday for Ryan Dougherty, the sheriff's office said.

Authorities provided a timeline for events surrounding the three siblings: On Monday, Ryan Dougherty was sentenced in Volusia County, Florida, to 10 years' probation and two years of community control monitoring for convictions on two counts of sending harmful information to a minor, the sheriff's office said.

After the Monday sentencing, he sent his mother a text message: "There's a time for all of us to die," according to the sheriff's office.

On Tuesday, at 6:30 a.m., a witness saw all three siblings leave in the white four-door vehicle from their Lacoochee home. At 6:59 a.m., Ryan Dougherty cut off his GPS monitoring ankle bracelet near Zephyrhills, the sheriff's office said.

At 7:12 a.m. Tuesday, the shooting with the Florida police officer occurred, in which 20 high-caliber casings were found at the scene, the sheriff's office said. The five-mile pursuit began after the officer tried to pull the vehicle over for speeding on State Road 54 in Zephyrhills, located 30 miles northeast of Tampa, Tobin said.

Then came the armed bank robbery at a CertusBank in Valdosta, Georgia, at 12:24 p.m. the same day, the FBI said.

During that robbery, three individuals dressed in black with masks entered the bank's front entrance, the FBI said. Shots were fired at the ceiling, and everyone was told to get down, the bureau said. At least two of the robbers were armed, and the third obtained an undisclosed amount of cash, the FBI said.

Lee Grace E. Dougherty's criminal background includes five felony charges. Three of them are pending, all of them hit-and-run offenses in Cocoa Beach, Florida, the Pasco County Sheriff's office said. Her record also contains six misdemeanor charges, the sheriff's office said.

The sheriff's office didn't have information on the disposition of the past charges against the brothers and sister.

The Pasco County Sheriff's office will seek a warrant Monday against Ryan Dougherty for failing to register as a sex offender in the county, the sheriff said in a statement. That registration was required after his sentencing this week for sending harmful information to a minor, Tobin said.